Dynamic modelling and simulation of a heated brine spray system

Abstract The aim of this work is to build a model of a heated brine spray system in order to predict its behaviour through dynamic simulation and thus optimize its performance. Concentrated brine solutions with initial temperatures from 65 to 85 °C are sprayed into the surrounding ambient air, in windy conditions. This spray system will be used in the NaCl salt recrystallization ponds that are integrated with a cogeneration unit, in order to increase the global process efficiency. This industrial platform is located in Pombal, Portugal, as already referred in a previous work [Moita, R. D., Matos, H. A., Fernandes, C., Nunes, C. P., & Prior, J. M. (2005). Dynamic modelling and simulation of a cogeneration system integrated with a salt recrystallization process. Computers and Chemical Engineering , 29 , 1491–1505]. A global three-dimensional mathematical dynamic model was built, which includes two models. The single drop model, which is based on the ballistics theory and includes material and energy balances, allows calculating each drop trajectory and velocity as it exits the nozzle, as well as its temperature, salt concentration and volume. The spray system model accounts for the full-cone spray-nozzle by considering a set of random defined drops. The spray system model was implemented and simulated in gPROMS 2.3.7. A sensitivity analysis of some model parameters and choices was performed. Model predictions, obtained through dynamic simulation, were compared with retrieved literature data, referring to water drops, in terms of drop trajectories and of evaporation rates. The model validation was also carried out using the experimental data obtained in the hereinabove mentioned NaCl recrystallization industrial ponds, referring to the respective heated brine spray system. It must be stressed that the simulated results are in reasonable agreement with the literature values and also with the experimentally measured ones. Although the model developed in this work allows predicting the behaviour of the mentioned heated brine scheme, it can be easily adapted to account for other types of systems and sprays.

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